Divisi
Smut
· Fungal
Photo: Björn S... · CC BY-SA 2.0
Smut is a family of fungal diseases (Ustilago and Sporisorium species) of cereals — maize, sorghum, pearl millet, wheat and barley. The fungus lives on seed and in the soil, sneaks into the young plant or an open flower, and grows unseen until flowering, when it turns kernels, cobs, tassels or grain-heads into swollen galls packed with sooty black dust (spores). Those spores fall to the soil and cling to seed, ready to start the disease again next season.
Holger Krisp · CC BY 3.0 
Nolanna · CC BY-SA 4.0
Why it matters
Smut attacks the part you harvest — it swaps your grain for a swollen bag of black powder, so every smutted head or cob is grain you will never eat or sell. A bad year can cost you up to a quarter of your crop (25%). Worst of all, there is no spray that cures a plant once the heads are infected — by the time you see the black galls the damage is done. Smut is only beaten by stopping it before it starts: with clean seed, resistant varieties and destroying galls before they burst and seed the soil for next year.
When to act
Any galls or smutted heads seen; smuts are managed pre-emptively because there is no rescue treatment once heads are infected.
This guidance is general, compiled from published agronomic references including FAO and CABI. Thresholds and timing shift with your crop, your variety and the season.
In much of the region a spray is simply called mushonga — medicine. But a chemical group you cannot name is one you cannot rotate, and a product you did not write down has no pre-harvest interval you can observe. Mushonga, and other farming words →
The full smut field guide
- Identify it
- Scout for it
- Control it
12 field-guide sections in the app
The full guide to smut — every symptom to check, how and when to walk your field looking for it, and the controls that actually work, ranked. Built into your crop plan, so you are told to look before it costs you a harvest.
Crops it affects
Frequently asked questions
How do I identify smut?
The damage you see first: at flowering and grain-fill, instead of normal cobs, tassels or grain-heads you find swollen, distorted lumps (galls) where the grain should be. On maize they look like shiny, silver-grey boils or blisters — some as big as a fist — on the cob, tassel or stem.
When should I take action against smut?
Any galls or smutted heads seen; smuts are managed pre-emptively because there is no rescue treatment once heads are infected.
How do I control smut?
Prevent first — this is where smut is won (start here every season): Plant a smut-resistant or tolerant variety suited to your crop — this is your strongest single defence. Always sow certified clean seed, never grain saved from a field that had smut. Rotate — plant a different, non-cereal crop on that land for a season or two so the soil spores starve with no host to infect. And keep the crop unstressed at flowering: avoid moisture and nutrient shortage at heading, because dry, hungry plants are the ones smut hits hardest.
Which crops does smut affect?
Among the crops covered here: Fonio, Maize, Pearl millet, Sorghum, Wheat.
Catch it before it costs you a harvest
Divisi builds scouting into your crop plan — it tells you when to walk your field, what to look for at that stage, and what to do when you find it. Free for farmers, works offline.
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